High-Selectivity Butyric Acid Production from Saccharina japonica Hydrolysate by Clostridium tyrobutyricum

Clostridium tyrobutyricum ATCC 25755 is a promising butyric acid-producing strain. However, the existence of acetic acid as a byproduct decreases butyric acid yield and increases downstream processing cost. In this study, we demonstrated that mannitol/glucose cofermentation with appropriate ratio (1:2 or 2:3) achieved high butyric acid yield (0.44-0.45 g/g) and selectivity (100%). To further improve the economic viability of butyric acid fermentation, we selected Saccharina japonica as a potential source of mannitol. The optimum condition (10% seaweed biomass in 0.11 M H2SO4 at 120 degrees C for 31 min) for mannitol release was identified through response surface methodology (RSM). After acid hydrolysis and enzyme saccharification, the feasibility of high-selectivity butyric acid production from S. japonica hydrolysate (supplemented with glucose to achieve a mannitol/glucose ratio of 1:2 and replaced (NH4)(2)SO4 with NH4Ac) was verified in the bioreactor, providing a promising approach for cost-effective production of biobased butyric acid.